07/23/2012 07:50 am ET | Updated Sep 22, 2012

What London Toilets And Cape Town Parking Lots Have In Common

I have more bad news about the U.S. economy. Three times, over two days, on two different continents, I couldn't give my American dollars away.

My first attempt was in London, where I had a 12-hour layover en route from Washington, D.C. to Cape Town, South Africa. So, with one red-eye flight completed, and one more to go, my boyfriend Steve and I embarked on a quick tour of London.

With only a few hours to spend, and very few operational brain cells, we opted for a double-decker bus tour of the city. As we bounced over cobblestone streets, our tour guide shared in-depth historical information about the city consisting of what parts of London appeared in the Harry Potter films. Another tour highlight was watching Prince William ride a griffin up the Tower of London -- though I may have dreamed that part, as I was drifting in and out of consciousness throughout the ride.

After about an hour, we hopped off the bus to look for a bathroom. There wasn't a Starbucks in sight, but I noticed a sign for a public loo -- and one that appeared to be relatively clean and free of permanent residents. Of course, it was too good to be true -- entrance cost 50p, and all I had was American money. Getting a bit desperate, and not knowing the exchange rate, I offered a British passerby what I thought was a generous trade: a dollar. He waved me off, so I upped my offer to two dollars. As he walked away, I tried to explain that, in America, toilets are free like the good Lord intended -- or at least available to anyone contemplating buying a frappuccino. Finally, a family of Belgian tourists took pity on me and gave me the change, without taking the dollar.

Twenty hours and 6,000 miles later, in Cape Town, I again failed to give away that dollar while trying to tip the guy who stands in the parking lot guarding your car. Perhaps you haven't heard of this service professional. I hadn't either, but it turns out that car-minding is a legitimate occupation in South Africa, where crime is a bit on the high side. Now, I consider myself to be a savvy city dweller, but what counts as street smarts here are turning out to be a bit different than what I'm used to. When I asked one local whether the trains are safe, she said, "Oh sure, of course! Just don't ride them at night." Then, her friend chimed in, saying, "And don't do anything flashy, like take out your cell phone or wallet." "Also, don't go anywhere by yourself," the woman concluded.

As for the car minders, the locals explained, it's customary to tip them about five rand to keep their friends from stealing your vehicle. Now that's about 60 cents, but my car minder must have had an inside tip on international money markets, because he flatly refused my dollar bill.

Tired of having my currency rejected, I finally visited a money-changer. For the remainder of my trip, I look forward to making liberal use of "public" restrooms and parking lots -- not interchangeably, I hope, though all bets are off if I'm short on change again.